This invention relates to a process for the production of 1,2,3-trichloro-2-methylpropane by reacting 3-chloro-2-methylpropene with sulfuryl chloride in the presence of aldehydes and/or under the effect of light.
In a conventional addition reaction, the reaction of 3-chloro-2-methylpropene with sulfuryl chloride yields 1,2,3-trichloro-2-methylpropane with a boiling range of 159.degree.-165.degree. C. in a yield of 83% (J. Am. Chem. Soc. 68: 787 [1946]). In this reaction, 3-chloro-2-methylpropene is charged into a reactor, and the reaction is performed with heating by the gradual addition of a stoichiometric quantity of SO.sub.2 Cl.sub.2 in total.
This reaction is unsatisfactory for an industrial process. On the one hand, the start of the reaction, after addition of a small amount of SO.sub.2 Cl.sub.2, is delayed and must be initiated by gentle heating; on the other hand, there is the danger that the exothermic reaction, after startup, will proceed uncontrollably. Moreover, the yield and selectivity leave a lot to be desired.
The addition of chlorine to unsaturated olefinic compounds by means of sulfuryl chloride can, it is true, be accelerated by adding peroxide or radical-forming agents (J. Am. Chem. Soc. 61: 3 432 [1939]), but this method is used only in special cases. Normally, the same addition products are also readily obtainable using elemental chlorine. The yields, however, range only between 80% and 90%.
Other conventional reactions for the production of 1,2,3-trichloro-2-methylpropane, such as the direct chlorination of isobutane or isobutene, or the further chlorination of suitable C.sub.4 chlorinated hydrocarbons such as, for example, 3-chloro-2-methylpropene, 1,3-dichloroisobutene, or 2-chloro-2-methylpropene proceed with even less selectivity. The end product of the process of this invention, 1,2,3-trichloro-2-methylpropene is useful for many purposes, e.g., as additional component for flame retardends or as a starting material for the preparation of the known compound cis- and trans-1-Chlor-2-methyl-propen-(1)-ol-(3), (Beilstein E III 1, p. 320) which is useful as derivating component for producing derivates of Cellulose and as pharmceuticals as described in C. A. 87 (1977) p. 579, 101874 q.